Since the Varroa mite reside especially in the drone brood in small cell bees and they are there even actively decimated by the bees (http://www.resistantbees.com/falle_e.html), will be seen how important the drone brood is for Varroa defense .

It is now early July and we had one month very little nectar flow, the bees flew barely and brood hatching decreased. The drone brood went back. Now is again beginning nectar flow at the coast, the wild fennel and the agave.
The bees have again very well laid brood:

and the drone brood is back again:

This is one of the major differences between small cell and large cell bees. The latter have only drone brood in spring and in the small cell bees the whole active year round, which is a huge advantage in terms of the Varroa mite. The drone brood is protecting the worker bee brood in the small cell bees.